The nature of concussion: a speculative hypothesis (original) (raw)
Related papers
Concussion in Professional Football: Brain Responses by Finite Element Analysis: Part 9
Neurosurgery, 2005
OBJECTIVE: Brain responses from concussive impacts in National Football League football games were simulated by finite element analysis using a detailed anatomic model of the brain and head accelerations from laboratory reconstructions of game impacts. This study compares brain responses with physician determined signs and symptoms of concussion to investigate tissue-level injury mechanisms. METHODS: The Wayne State University Head Injury Model (Version 2001) was used because it has fine anatomic detail of the cranium and brain with more than 300,000 elements. It has 15 different material properties for brain and surrounding tissues. The model includes viscoelastic gray and white brain matter, membranes, ventricles, cranium and facial bones, soft tissues, and slip interface conditions between the brain and dura. The cranium of the finite element model was loaded by translational and rotational accelerations measured in Hybrid III dummies from 28 laboratory reconstructions of NFL impacts involving 22 concussions. Brain responses were determined using a nonlinear, finite element code to simulate the large deformation response of white and gray matter. Strain responses occurring early (during impact) and mid-late (after impact) were compared with the signs and symptoms of concussion. RESULTS: Strain concentration "hot spots" migrate through the brain with time. In 9 of 22 concussions, the early strain "hot spots" occur in the temporal lobe adjacent to the impact and migrate to the far temporal lobe after head acceleration. In all cases, the largest strains occur later in the fornix, midbrain, and corpus callosum. They significantly correlated with removal from play, cognitive and memory problems, and loss of consciousness. Dizziness correlated with early strain in the orbital-frontal cortex and temporal lobe. The strain migration helps explain coup-contrecoup injuries. CONCLUSION: Finite element modeling showed the largest brain deformations occurred after the primary head acceleration. Midbrain strain correlated with memory and cognitive problems and removal from play after concussion. Concussion injuries happen during the rapid displacement and rotation of the cranium, after peak head acceleration and momentum transfer in helmet impacts.
A new biomechanical assessment of mild traumatic brain injury. Part 2: Results and conclusions
2000
This paper follows Part 1 that was presented at the 1999 IRCOBI conference. A methodology, described in Part 1, has been developed that permits the reconstruction of certain incidents that occur in American football. Twenty-four cases of helmeted head impact, for which concussion was diagnosed in 9 cases, have been replicated with Hybrid III Anthropometric Test Devices (ATDs). Rigid body translational and rotational head accelerations have been measured in each case. Correlations between head injury and head kinematics have been sought. Peak translational and peak rotational acceleration and velocity, Head Injury Criterion (HIC) and the C.W. Gadd Severity Index (SI), as well as the GAMBIT have all been considered. A new approach employing the maximum value of the global rate of energy dissipation has proven to provide the best correlation between concussion probability and head kinematics. This new relationship provides a basis for a new HIC function, the Head Impact Power (HIP).
Concussions and their consequences: current diagnosis, management and prevention
Canadian Medical Association Journal, 2013
C oncussion is the most common type of mild traumatic brain injury and can have serious consequences. Not just confined to high-profile athletes, concussions are frequent in all age groups and in a variety of settings, such as the work environment, motor vehicle crashes, sports and recreation, and falls at home among older people. Concussion is defined by the International Consensus Conference on Concussion in Sports as "a complex pathophysiological process affecting the brain, induced by biomechanical forces." 1 Concussion is the preferred term be cause of its familiarity to the public. Since 2000, international expert panels have clari fied the definition and modified the management of concussion; these changes have affected recommendations for return to work, school and sport for those experiencing a concussion. 1,2 The importance of accurate and timely recognition and management stems from the consequences of misdiagnosis or faulty management that can lead to major disability or death, in both the short and long term. Second-impact syndrome occurs when a concussed person, especially a younger person, returns to play before complete recovery and sustains a second brain injury. However, malignant brain swelling can occur even without a second injury. 3 Also, repeated concussions may cause delayed posttraumatic brain degeneration, leading to dementia and movement disorders similar to Alzheimer and Parkinson diseases. 4 Thus, it is important for practitioners to know the current principles of recognition and management of concussions, including the physical, cognitive and emotional effects and the guidelines for return to play, work or school. Mechanism The exact mechanism of concussion is unknown. Axon tearing occurs in more severe brain injuries, but proof is lacking for this mechanism in concussion. It is more likely that concussion is due to rotational acceleration of the brain (jiggling of the brain) 5 that produces a disordered metabolic cascade or biochemical injury such as altered metabolism of glucose or derangement of adenine nucleotides. 6 It is still uncertain where in the brain concussion occurs, or the exact origin of the symptoms of acute concussion. It is now apparent that direct impact to the head is not required: concussion can occur with a blow to the chest, for example, that causes a whiplash effect on the brain. Whiplash of the neck and concussion frequently co-exist. 7 Risk factors The young brain is more susceptible to concussion than the adult brain and may require more time to recover. 8 Also, it is now known that, after a concussion, there is greater susceptibility to sustaining another concussion and that subsequent concussions occur with less force and take longer to resolve. 9 New information indicates that females may be more susceptible to concussion than males 10 and that there may be a genetic factor underlying susceptibility to concussion. 11
Traumatic Backing Insufficiency: The Need for More Concussion Research (Sophomore Research Paper)
2016
subarachnoid space is the arachnoid, which does not adhere to the shape of the brain, and is thus like a loosely fitting sac on the exterior of the brain (The Editors of Encyclopaedia Britannica, 2016). Closest to the skull is the dura mater, which is a thick membrane composed of dense fibrous tissue (The Editors of Encyclopaedia Britannica, 2016). Surrounding the dura are two potential places for blood to pool during a brain hemorrhage: The epidural space, which is superior to the dura, and the subdural space, which is anterior to the dura (McAffrey, 2014).
A common neural signature of brain injury in concussion and subconcussion
Science Advances
The midbrain is biomechanically susceptible to force loading from repetitive subconcussive head impacts (RSHI), is a site of tauopathy in chronic traumatic encephalopathy (CTE), and regulates functions (e.g., eye movements) often disrupted in concussion. In a prospective longitudinal design, we demonstrate there are reductions in midbrain white matter integrity due to a single season of collegiate football, and that the amount of reduction in midbrain white matter integrity is related to the amount of rotational acceleration to which players’ brains are exposed. We then replicate the observation of reduced midbrain white matter integrity in a retrospective cohort of individuals with frank concussion, and further show that variance in white matter integrity is correlated with levels of serum-based tau, a marker of blood-brain barrier disruption. These findings mean that noninvasive structural MRI of the midbrain is a succinct index of both clinically silent white matter injury as wel...
Estimated Brain Tissue Response Following Impacts Associated With and Without Diagnosed Concussion
Annals of biomedical engineering, 2018
Kinematic measurements of head impacts are sensitive to sports concussion, but not highly specific. One potential reason is these measures reflect input conditions only and may have varying degrees of correlation to regional brain tissue deformation. In this study, previously reported head impact data recorded in the field from high school and collegiate football players were analyzed using two finite element head models (FEHM). Forty-five impacts associated with immediately diagnosed concussion were simulated along with 532 control impacts without identified concussion obtained from the same players. For each simulation, intracranial response measures (max principal strain, strain rate, von Mises stress, and pressure) were obtained for the whole brain and within four regions of interest (ROI; cerebrum, cerebellum, brain stem, corpus callosum). All response measures were sensitive to diagnosed concussion; however, large inter-athlete variability was observed and sensitivity strength...
Neurology
In American football repetitive brain trauma is associated with high risk of neurologic disorders. Head contact is integral to the game, resulting in high frequency of head contacts during a game/season. Low energy impacts that do not manifest signs recognized as injury still present metabolic and/or physiologic changes within the brain. The purpose was to estimate player position specific brain trauma profiles based on strain magnitude and impact frequency. Head impacts from 32 game films of professional football were documented and categorized based on event type, head location, and velocity for 8 positions. Inbound velocity was calculated using Kinovea 0.8.20 software. Events were reconstructed using 50th percentile Hybrid III headform, unbiased neckform, linear impactor (collisions) and monorail drop tower (falls). Maximum principal strain (MPS) within the cerebrum was calculated using UCDBTM. Frequency [p < 0.0005] and magnitude [p < 0.0005] were significantly different between the 8 positions. No significant differences in frequencies between the following; quarterback, wide receiver, and defensive back; running back, tight end, and linebacker; and between offensive and defensive linemen. Approximately 60% of documented impacts were received by linemen and tight end. The magnitudes of impacts experienced by quarterbacks were significantly different to all positions excluding wide receiver and defensive back. Wide receiver experienced significantly different magnitudes than both linemen; and differences were found between offensive linemen and defensive back. Approximately 95% of impacts experienced by linemen were below 17% MPS. Conversely, over 90% of impacts documented for quarterback were above moderate strain magnitudes (>17%). Results show risks of repetitive trauma and injury vary with position; some experience high frequency impacts of low magnitude while others receive lower hit counts of higher magnitudes. Findings showed that tight end and running back are particularly risky with relatively high brain strain magnitudes coupled with high frequency making them susceptible to high trauma loads.